I recently bought Heart Throbs #102 off of ebay in VG condition for about $8. I'm sure if you're patient you'll find an affordable copy.

Well, I managed to pick up the first part for both the major serials.
Secret Hearts #110 and Heart Throbs #102.
You were right it just takes a bit of patience.
Still it will take quite some time before I find reasonable copies of all parts for these serials,
but I'm sure I'll get there.